The present invention relates generally to an improvement of a magnetic recording medium applicable as magnetic disks, in which a metallic magnetic film is formed on a nonmetallic substrate such as ceramics, glass or their composite material via a metallic magnetic film-supporting base layer (referred to as base layer, hereinafter), and more specifically to a magnetic recording medium provided with an excellent durability against magnetic head contact-start-stop operation by forming an intermediate layer between the nonmetallic substrate and the metallic base layer to prevent peeling-off of the metallic base layer.
Magnetic disks have been widely used as storage devices in various information processing systems such as computers. In order to improve the information processing ability, recently higher density and larger capacity are both required for the magnetic disk devices, and therefore metallic films formed by sputtering or ion plating technique have been in the course of practical use as magnetic recording layers of the magnetic disks.
In general, an aluminum alloy plate onto which Ni-P plating is applied is used as a substrate for the magnetic recording medium; however, it has been reported that there exist various problems such that the substrate itself suffers elongation by high speed disk revolution, and errors in writing/reading due to thermal expansion, etc. Further, since the Ni-P plating layer is generally formed by wet plating it has been known that moisture or various ions usually remain in the plated layer, thus resulting in corrosion of the metallic base layer and the magnetic layer and therefore to offer causes for said errors.
To overcome the above-mentioned problems, a magnetic disks in which a reinforced (tempered) glass or various ceramic substrates are used has been proposed, and further a magnetic disk in which a magnetic layer is formed on a ceramic substrate via a glazed layer has been proposed (in Japanese Patent Kokai Publication No. 60-138730).
In the magnetic disk in which a metallic base layer and a magnetic film are laminated on the various nonmetallic substrates as described above, peeling-off between the nonmetallic substrate and the metallic base layer often occurs due to strain caused by a difference in the thermal expansion coefficients between the nonmetallic substrate and the metallic base layer, or through friction or impact between a magnetic head and the magnetic disk in use particularly when the magnetic head starts or stops on the disk, thus causing errors in the writing/reading operation. In addition, it would result in a serious problem as so-called drop-out of memory.
Further, as a method of solving the above-mentioned peeling-off problem on the metallic base layer, a metallic substrate (e.g., aluminum substrate) in which the peeling-off is to be prevented by intervening a coexistent area between a nonmagnetic metallic substrate and a metallic base layer has been disclosed in Japanese Patent Kokai Publication No. 61-54016. However, this technique cannot solve the aforementioned drawbacks peculiar to the metallic substrate, and further is not applicable to a method for preventing the peeling-off between the nonmetallic substrate and the metallic base layer. In summary, there exists a strong demand for preventing the peeling-off of the metallic base layer from the nonmetallic substrate.